On Wednesday 09 September 2020 13:41:53 Jon Elson wrote: > On 09/09/2020 12:16 PM, Gene Heskett wrote: > > On Wednesday 09 September 2020 12:38:43 Jon Elson wrote: > >> On 09/09/2020 11:08 AM, Gene Heskett wrote: > >>> Is it possible to get an enable signal, per axis, from the mesa > >>> cards that would become true, hopefully a couple micky-secs ahead > >>> of the first stepper pulse so no missed steps would normally > >>> occur, losing its home, and go back false when the last step has > >>> been sent? It maybe could be timed right if it actually steps on > >>> the trailing edge of the pulse, and the enabling action was on the > >>> leading edge. > >> > >> This is the TRICKY bit, knowing when an axis is SOON going > >> to start moving. > >> > >> Jon > > > > I'd be surprised if these things needed any lead time at all, Jon. > > The hitachi docs on this chip do not mention any timing constraints > > in regard to this. So its likely that it could be brought up to full > > song with the leading edge of the pulse. If that triggered a > > retriggerable oneshot that was then or'd with the pulse, and its > > output would be the enable high current signal. Let the oneshot time > > out in 50 millisecs if no pulse, putting it back in reduced current > > at the end of the move. If the oneshot was in the mesa, would be > > ideal, and divorced from the enable granularity of the 1khz servo > > thread. That granularity could easily lose enough steps to destroy > > a home position, something I intend to have with this BS-1 clone. A > > oneshot in the hal file would be a disaster in that case because of > > the millisecond+ delay. A oneshot in the cable to the driver would > > work, but if its in the mesa card, better yet. :) > > Certainly worth a try. One horrible possibility is that the > DIP switches are only read once at > power-up. The first couple steps should be spaced out as > the axis accelerates which should give the drive time to > ramp up the current. > > Jon
Nah, I can change them while its running, and hear the change in the motors sound as the currents change in real time. But thats not saying that some other board using this power chip might not do it differently. These came out of the electrics box that came with a 6040 gantry mill I paid $1175 for, very carefully designed so as not to be used by anything but the very limited Mach3. The vfd for instance, has a reverseing input. It ignores it. It also has an analog speed input, also ignored, forcing you to use only that mode where the front panel knob is active. Then, finding the motor supply was duff, I said to hell with this and went to the shop, coming back with the driver kit from my broken hf mill. Runs it well, add another ebay clone of a decent vfd and it all Just Works, x&y at 192 ipm, z at 35 ((needs more motor to lift a 1.5 horse water cooled spindle) and A at about 15 rpm. Turn on the mister, and carve the panels for the interface box, 12 holes Plus a line cord grommet, in about 3m:30s. And doesn't sound like its working all that hard. Thanks Jon. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
